A novel photoinduced self-substitution reaction of dichloro-1,4-benzoquinones in the presence of certain aliphatic tertiary amines

Abstract

A series of novel compounds has been obtained from the photoinduced self-substitution reactions of 2,5-, 2,6- and 2,3-dichloro-1,4-benzoquinones in the presence of certain hindered N,N-dimethyl-alkylamines, i.e. N,N-dimethyl-tert-butylamine, N,N-dimethyl-4-phenylbicyclo[2.2.2]-1-octylamine, N,N-dimethyl-1-methylcyclohexylamine, and N,N-dimethylcyclohexylamine. The main products were dimer 4a, trimer 5a and pentamer 6 from 2,5-dichloro-1,4-benzoquinone, dimers 4b and 4c and trimer 5b from 2,6-dichloro-1,4-benzoquinone, and trimer 5c from 2,3-dichloro-1,4-benzoquinone respectively. A mechanism involving photoinduced electron transfer from the amine to the dichlorobenzoquinone (Q) as the initial step is proposed for the reaction on the basis of photo-CIDNP and electrochemical experiments.